#Mt. Fiddler:  I wouldn't go cutting into your bow.  They make gadgets for "pinky positioning" or whatever one might call it.

qid=1360256235&sr=8-5&keywords=violin+bow+nest

...and while that isn't by any means expensive, I personally wouldn't pay that for what it is.  You could probably make one in 5 min out of an old marker cap. 

Nothing wrong with trying a gadget or gimmick once in a while though.  At least it can be a fun experiment.  Sometimes they probably can even help, at least briefly, to form new habits or something.  If they do, fine and well.  If they don't, then at least you know about them when someone else asks.  If you see any benefit from it, I'd bet that like most gadgets, it would outlive it's usefulness in a few days for you.  Probably less days than you'd wait for it to come in the mail.

To replace even a cheap bow costs more than that gadget.  And the gadget costs more than a marker cap (or anything else that happens to be lying around that is about the right size, like a piece of tubing or whatever).  So, use a little Yankee ingenuity and cobble one together and see if you feel it helps.

Silly as such things may seem, I've known some good martial artists and body builders who would try every weird goofy gadget they could find.  Never know when one might actually be useful or even just be that little bit it takes for a few days to break into a new plateau.  Failing that, it was at least something to have a little fun goofing around with.  A little variation in the practice routines.

With the talk about the "pinky nest" gadget, I decided to try cobbling something like it together, just to see what it actually does (and if it might be useful for my own practice/playing).  Easy to just dismiss any new gadgets, but unless one has actually tried something at least similar, it is just "talking though your hat". 

My first attempt was with a bit of heavy copper wire I had handy by the computer.  12 gauge, I think. 

I noticed when trying it that having the pinky curving down onto that spot was different than how I usually had been holding the bow.  My pinky had been resting usually near or on the adjustment knob, and this was closer to the frog.  But my design/version slid on the stick too easy, and I figured the metal would likely mar up the wood, so I took some plastic tubing I had handy and made one more like the commercial "pinky rest".

More stable, less likely to mess up the stick or frog, and it positions the pinky more where FM shows in the tutorial on how to hold the bow.

But I was pretty sure I'd seen some pics and tutorials with the pinky placed a bit further back than FM shows it.  Checking my older bookmarks, I found some, including Itzhak Perlman's vid on Bow Grip where it was a little further back, but not as far back as I had been putting it.  So there might be some variance for hand size.  I have rather large hands, but Mr. Perlman is pretty well known for having large hands for a violinist, and I doubt I need to move the pinky back further than he does.  So I made yet another one that places the pinky about where Itzhak says to.

Interesting stuff.  I think the gadget maybe could actually be helpful for some folks.  In my own case, I'm pretty sure it corrects some aspects of an incorrect bow hold.  I *thought* I was holding it like I'd seen shown months ago in assorted video tutorials, but my pink had apparently drifted down towards the end of the stick which was maybe spreading the hand too much.  With the gadget, I notice that a much gentler bow grip is actually comfortable, and the bottom end of the bow stroke seems a bit less of a strain to the wrist.  It also seems to fix a bad habit I have of locking my bow-hand thumb with the joint bent backwards.  I've been working on that for quite a while, but it kept locking like that whenever my attention would be on some other aspect of playing.

That's an example of where lessons/teachers can be good, if you can manage it.  A teacher would have probably spotted it months ago and figured out what I could be doing better. 

In any case, I'll try both the FM/commercial "pinky nest" position and the Itzhak position for the pinky for a bit in my practices and playing and see how it goes.  But just from a brief test of how it feels to play using something like one of these little gadgets, they may actually be useful to develop the habit/muscle-memory of having the pinky in a spot which may be a bit better than what I have been doing.  

My pic here show a couple ways of going about it without actually running out and buying or ordering the gadget, and of course there would be other ways it can be done as well.  Might be worth a try, though.

@Dude-CCK:  I use it like this..

Pretty simple.  The one I made weighs around 1 gram.